The present embodiments relate to magnetic resonance imaging (MRI). In particular, clinically relevant biomarker images derived from diffusion MRI are provided at a greater resolution. Diffusion MRI may describe the white matter architecture in vivo by quantifying variations in water diffusion in the brain.
Diffusion weighted MR images (DWIs) acquired using conventional MR scanning protocols are often limited by insufficient spatial resolution. Several diffusion biomarkers/maps (e.g., fractional anisotropy) can be derived from the DWIs using, for instance, the diffusion tensor (DT) model. The biomarker images are desired to be in a higher resolution than the scan resolution for better visualization of the structural brain connectivity and its impairment, if present, due to neurological diseases. However, conventional interpolation/upsampling of the biomarker images does not yield anatomically accurate and reliable results.
Diffusion MR image resolution has been enhanced using processes applied before or after fitting a diffusion model to the DWIs. In some approaches, multiple DWI scans acquired along a number of orthogonal through-plane axes stitched with non-linear registration are used. These approaches seek to increase the resolution of the raw data, not directly increasing the resolution of the biomarker images clinicians prefer to visually investigate. In another approach, extracted white matter fiber pathways are used to compute higher-resolution diffusion maps from the ‘track density’ information. However, this approach may be heuristic (i.e., non-reproducible) and by definition, prone to the errors in tractography.